The objective of this award is to provide the applicant with the experience, mentoring and knowledge necessary to become an independent health services researcher in the field of diagnostic errors in cancer. Diagnostic errors are likely the most common type of error in primary care and are the most expensive. Missed and delayed cancer diagnoses are particularly frequent, harmful and costly. Errors in cancer diagnosis are poorly understood and difficult to study. Although diagnostic errors have been shown to have both systems and cognitive origins, there is no comprehensive theory of medical diagnostic problem-solving that addresses both types of factors. However, the situational awareness framework used in aviation safety research encompasses cognitive and system origins of pilots'decision-making errors and may offer solutions to improving the diagnostic process as well. Situational awareness precedes and is critical to effective decision-making, a key element in conceptualization of a correct diagnosis. The research goal is to use the situational awareness framework, which has the potential to address both systems and cognitive origins of medical decision-making errors, to identify key determinants of missed and delayed breast, lung and colon cancer diagnoses. The overall hypothesis is that the situational awareness framework can be used to identify the major cognitive and systems vulnerabilities in the diagnostic process and to suggest future targets for improvement. In preliminary work, the applicant has used this framework to study the process of diagnostic decision-making in cancer. Taking advantage of interdisciplinary resources from several institutions in the Texas Medical Center, collaborative expertise from the National Aeronautics and Space Administration, and clinical scenarios available through a National Cancer Institute-funded consortium, the specific aims are: Aim 1: To use the situational awareness framework to retrospectively identify the major system factors that lead to diagnostic errors in cancer. Aim 2: To use the situational awareness framework in a simulated setting to prospectively identify the major cognitive errors in cancer-related diagnostic decision-making. Aim 3;To study prospectively the effects of cognitive and system factors and their interplay on situational awareness in diagnosis of cancers in real clinical settings. The applicant has extensive clinical experience and is currently obtaining basic research skills through an NIH-funded K30 program. To achieve his goal of understanding and reducing diagnostic errors he needs advanced research skills and mentored training in specific content disciplines. A highly qualified interdisciplinary advisory team will supervise training that will include mentored research, formal coursework, directed readings and seminars. The proposed activities will provide a multidisciplinary foundation to reduce diagnostic errors in cancer and will provide the applicant with the experiences and skills he needs to achieve independence in a health outcomes research career focused on cancer diagnoses.